Abstract

With the aim of enhancing pool boiling heat transfer coefficient (HTC), the nucleate boiling performance of nanoporous surfaces obtained by an electrophoretic deposition (EPD) method is evaluated in this paper, with SES36 as the boiling fluid. A pool boiling experimental apparatus and procedure are described. Three kinds of experiment have been performed: (i) smooth stainless steel (SS) surface with pure SES36, providing the baseline; (ii) smooth SS surface with boiling nanofluid consisting of 0.5, 1 and 2 wt% Al2O3 suspended in SES36; (iii) nanoporous surfaces, of SS coated by EPD in procedures using 0.5, 1 and 2wt% concentrations of Al2O3, with pure SES36 as the boiling fluid. In (ii), the results show that the HTC of the smooth SS surface deteriorated with increasing concentration of Al2O3. In (iii), however, the HTC increased by approximately 6.2%, 30.5% and 76.9% for surfaces prepared with suspensions containing 0.5, 1 and 2 wt% Al2O3 respectively under the heat flux of 90 kW/m2, compared with the baseline of the smooth surface in (i). The boiling behaviors are related to the modified surface micro-morphology due to the deposition of nanoparticles, as visualised by scanning electron microscopy (SEM). The maximum active nucleation site density was about 2.6×105 sites/m2 for the 2 wt% EPD surface under 94 kW/m2, which is 1.8 times of the smooth SS surface. The increased site density of the nanoporous surface obtained by EPD enhanced greatly the nucleate pool boiling.